Polarimetric Behavior for the Derivation of Sea Ice Topographic Height From TanDEM-X Interferometric SAR Data

Abstract

Single-pass interferometric synthetic aperture radar (InSAR) is an effective technique for sea ice topographic retrieval despite the inherent dynamics of sea ice. However, the penetration of microwaves into snow-covered thick ice and the achievable height sensitivity for tens-of-centimeters thin ice are two major issues, which limit the accuracy of InSAR-derived sea ice topography. Polarimetry provides scattering information concerning the sea ice properties and has the potential, in combination with interferometry, to achieve an accurate reconstruction of a sea ice digital elevation model (DEM). This article studies the relation between polarimetric signatures and sea ice topography, and explores the possibility to compensate the penetration bias by merging copolar coherence into InSAR processing. The newly generated topographic map has a root-mean-square error under <inline-formula><tex-math notation= LaTeX >$0.3\\,\\text{m}$</tex-math></inline-formula>. For thin ice below <inline-formula><tex-math notation= LaTeX >$1\\,\\text{m}$</tex-math></inline-formula>, a positive relation between copolar phase <inline-formula><tex-math notation= LaTeX >$\\phi _{\\text{coPol}}$</tex-math></inline-formula> and surface height is observed, suggesting that <inline-formula><tex-math notation= LaTeX >$\\phi _{\\text{coPol}}$</tex-math></inline-formula> can effectively characterize thin sea ice topography. For thick ice with ridges, the maximum polarimetric phase difference <inline-formula><tex-math notation= LaTeX >$\\Delta \\phi _{\\text{maxPol}}$</tex-math></inline-formula> reveals a particular shape of the coherence region, which can be interpreted as oriented volume scattering. It suggests that the model-based approach using polarimetric SAR interferometry assuming an oriented volume scattering model is promising in measuring the scattering centers in thick and deformed sea ice. The study of polarimetric behavior for the InSAR DEM is, therefore, a step forward toward accurate modeling of sea ice topography from polarimetric single-pass InSAR data.